Digital computers on recent airplane models require frequent software updates. Flight management computers (FMCs) were among the first of these computers to have periodic updates performed. Originally, these updates were performed according to a tape loading standard (ARINC 603) that required the use of a portable device having one ARINC 429 output and two inputs. The loading was performed by attaching a cable and a portable tape loader to a 32-pin data loader connector located in the cockpit of the airplane. The location of this connector was chosen in different model airplanes to avoid having a mechanic crawl around an electrical equipment (EE) bay each time he was required to perform a software update. Nevertheless, it was soon recognized that portable tape loaders were slow, large and cumbersome. Thus, a new data loading standard, ARINC 615-1, was developed to utilize standard 3½″ floppy disks.
To accommodate new ARINC 615-1 loaders, the 32-pin data loader connector was replaced with a new 53-pin connector. In addition, some airlines preferred that loaders be configured for permanent mounting on primary long haul aircraft. As a result, the ARINC 615 specification was upgraded to accommodate additional busses in an attempt to anticipate a maximum number of loadable units that would require an interface with an ARINC 615 loader. Today, as many as 24 loadable Line Replaceable Units (LRUs) may be found on a single aircraft. However, only eight LRUs can be accommodated by the ARINC 615-3 specification.
One solution to the increasing number of LRUs on an aircraft has been to provide a Portable Data Loader (PDL) connector with a multiple position rotary switch. In some cases, approximately 200 wires populate four circular connectors located on the data loader switch installed on a maintenance panel.
Data communication between aircraft and ground began using existing HF and VHF radios to transmit character data stored in a few avionics line replaceable units (LRUs). The routing of information such as central maintenance computer and aircraft condition monitoring system reports in one known data communication system is under control of a management unit (MU) based on ARINC 724 specifications. The interfaces through which data has been routed from aircraft systems are traditional analog discrete and ARINC 429 data bus interfaces.
As the complexity of aircraft communication and reporting systems (ACARS) have increased, production aircraft have been provisioned with more advanced versions of such systems based on ARINC 758 specifications. One such communication management unit (CMU) is capable of handling protocol layers beyond those specified by ARINC 724B. One known CMU is also intended to accommodate interfaces to Ethernet-based systems, adding an additional, non-traditional physical layer. Digital link radios currently in development would further improve transmission between ground stations and aircraft. However, bandwidth for this technology still lags that provided by broadband satellite data communications.
ARINC 758 CMU functionality manages the routing of data for aircraft avionics systems over data link radios and satellite communication systems (SATCOM), with expandability to Ethernet-compatible systems. Sources and end users for communication with a ground station include satellite data units (SDUs), ACMS, central maintenance computers (CMCs), and optional cabin terminals via HF, VHF, SATCOM, and new data link radios. Aircraft information to the CMU comes from many avionics sources, such as display systems, flight management computers (FMCs), DFDAU digital discretes, ACMS, DFDAU ARINC 753 data, out/off/on/in (OOOI) discretes and transponders. Two-way communication is also established between multifunction control and display units (MCDUs), printers, data loaders, and aircraft programmable modules (APMs). CMUs are also capable of driving up to two sets of alert output discretes.
The aircraft industry is currently developing ARINC 763 Network Server Systems (NSS), which will have management capability for routing information over IEEE 802.11 transceivers utilizing wireless spread spectrum technology as well as Ethernet interface capability. The primary avionics data sources that ARINC 763 systems require are aircraft parametric information and 2-way ARINC 429 communication directly between avionics LRUs and a server interface unit (SIU).
As currently envisioned, ARINC 763 NSS will acquire parametric data and status via an ARINC 573/717 serial output of a digital flight data acquisition unit (DFDAU). To update software in avionics LRUs, the SIU is wired upstream from a rotary switch, between the switch and an existing portable data loader connector or an installed airborne data loader. However, one problem with designs of this type is that only raw parametric data out of the DFDAU is available. Processed reports, based on re-configurable capture criteria in ACMS, e.g., operator selectable channels of smart access recorder (SAR) data, re-programmable ACMS triggered reports, in addition to raw data intended for quick access recorders (QAR), are only available via an ARINC 615-3 data loader interface to the ACMS, and can be retrieved on-ground via disk download, or via ACARS as a defined trigger-event occurs.
A primary goal of aircraft manufacturers is to minimize changes to aircraft production processes while at the same time offering increased functional capability and ease of use in new product offerings. When numerous new wiring, LRUs and supporting components are added to production aircraft, aircraft manufacturers incur large, non-recurring costs. To avoid drastic changes that would incur these large costs, ARINC 763 NSSs are being designed with a limited subset of traditional aircraft interfaces. For example, one known ARINC 763 NSS is being designed to tie into two primary interfaces. The first of these two interfaces is an ARINC 573/717 DFDAU serial output bus to an existing QAR interface or parallel ARINC 573/717 path. The second is an existing data loader interface. NSS designers thus minimize usage of aircraft information from different aircraft sources and add a new communication medium to the aircraft information routing scheme, namely, wireless IEEE 802.11. Thus, some data movement issues on the aircraft side remain and some existing features, available in other known avionics LRUs, are not fully utilized.
Also, ARINC 758 and ARINC 763 systems have different philosophies regarding routing of aircraft information. ARINC 753 systems are connected to many existing aircraft interfaces with air/ground and limited ground/ground communication via existing radio and satellite technology. On the other hand, ARINC 763 systems are being designed for connection to a very small number of aircraft interfaces with ground to ground and limited air to ground communication (depending upon the distance to an access point) using wireless spread spectrum IEEE 802.11 communication technology. Known systems do not provide integration of these routing functions.
Present maintenance practices for downloading aircraft data into Avionics line replaceable units (LRUs) include using a portable or PC-based ARINC 615-3 data loader to download part number controlled databases, operational program configuration (OPC) files, and operational program software (OPS) that is ordinarily transferred using 3¼″ floppy disks. A permanently mounted airborne data loader (or a bulk loader in a shop environment) can also be used to load aircraft LRUs.
Software loadable LRUs in at least one aircraft line can be downloaded with controlled information stored on floppy disks. The loadable data conforms to ARINC 615 data formatting standards by including a CONFIG.LDR header file, embedded load cyclic redundancy checks (CRCs), system address labels (SALs), and a data bus sequence, and conforms to other file structure requirements. Avionics systems currently installed in this aircraft line provide two-way communication using standard ARINC 615-3 protocol, and this protocol is used on all LRUs that require periodic software upgrades. Wiring to accommodate LRUs that use the ARINC 615-3 protocol are routed to an existing multi-deck rotary switch. In a typical Boeing 747-400, for example, up to 23 LRUs utilize this upload function. A human operator uses the rotary switch to provide connectivity between avionics units to an airborne data loader or to a connector of a portable data loader. The wiring to the switch passes from an electronics equipment (EE) bay to a centralized flight deck location.
Because of the need for manual intervention to operate switches to provide connectivity between avionics units, providing automatic uploads of avionics data from aircraft to ground stations via wireless communication links would require extensive rewiring of existing aircraft. Remotely-initiated download of data from ground stations to aircraft would also require extensive rewiring.